Tumor associated carbohydrate antigens (TACAs) are over expressed on the surface of cancer cells and related to tumor cell adhesion and metastasis.1 Thus. TACAs are potential targets for cancer vaccine development.2 However, most TACAs have poor immunogenicity and many approaches have been developed to increase the immune response of carbohydrate-based vaccines, including conjugation with a carrier protein3, administration with an immunologic adjuvant4, using unnatural glycosidic linkage5, clustered antigens6, unimolecular polyvalent vaccine7 or hetero-glycan multivalent vaccine8. Using these strategies, a few carbohydrate-based vaccines that could elicit significant immune responses to target glycan structures were designed for cancer therapy and entered clinical trials.3,9 Among them, the clinical trials of Theratope and GMK with adjuvant QS-21 failed to produce statistically significant difference between time-to-disease and overall survival rate. Probably these two vaccines could not elicit robust T cell-dependent immune response in patients.10 Specifically, Theratope and GMK induced a higher level of IgM in patients but could not induce a strong immune IgG response, which is a major problem in carbohydrate-based vaccine development.11 
Globo H (GH; Fucα1→2Galβ1→3GalNacβ1→3Galα1→4Galβ1→4Glc) is a member of the globo series glycosphingolipids. It was first found and characterized in human teratocarcinoma cells and breast cancer MCF-7 cells in 1983,12 and was subsequently found overexpressed in many types of human cancer cells including breast, prostate, ovary, pancreas, brain, endometrium, gastric, colon and lung cancers.13 A Globo H vaccine using KLH as carrier and QS-21 as adjuvant prepared by Livingston and Danishefsky showed a positive result in a phase I study against metastatic breast cancer patients.14 With improvement in synthesis15, it is now in phase III clinical trial in Taiwan and phase II clinical trial in the USA, Korea, Hong-Kong and India for late stage breast cancer patients and in phase II clinical trial for ovarian cancer patients in Taiwan. However, these early stage clinical results showed that the induced IgM antibodies were still much higher than IgG antibodies.14,16 Recently, our group has developed a better vaccine using diphtheria toxoid cross-reactive material (CRM) 197 (DT) as carrier and a glycolipid C34 as adjuvant to induce a class switch with robust IgG antibody response against GH, its fragment Gb5 and SSEA4, all found on breast cancer cells and the cancer stem cells only.13b 
Previous studies showed that modification of carbohydrate antigen structures (MCAS) could effectively elicit a higher level of immune response.17 For example, in the modification study of the capsular polysaccharide of group B meningococci, the N-acetyl groups of α-(2,8)-linked polysialic acid (PSA) was replaced with the N-propinoyl group and such a modification elicited a high antibody response to recognize not only the N-propinoyl PSA, but also the nature N-acetyl PSA.18 Similar approaches were applied to STn19 and GM320 antigens to produce high antibody titers against modified and nature forms. The results indicated that N-phenylacetyl, N3, N-fluoroacetyl or N-difluoroacetyl modifications on glycan antigens could improve the immunogenicity.19a,c Moreover, the Schultz group reported that incorporation of a p-nitrophenylalanine into the tumor necrosis factor-α (TNF-α) could break immune tolerance and induce more antibody response to TNF-α.21 Using glycans as antigens, although some progress has been achieved, most cases are the N-modification of disaccharide (STn), trisaccharide (GM3) and polysialic acid (PSA) and some are based on fluorinated MUC1 glycopeptide antigens.18a,19a,d,20,22 There is a lack of a general strategy for the preparation of carbohydrate-based vaccines to induce IgG response with a long-term memory.